How does thermal pressurization of pore fluids affect 3D strike-slip earthquake dynamics and ground motions?

Abstract

Frictional heat during earthquake rupture raises the pressure of fault zone fluids and affects the rupture process and its seismic radiation. Here, we investigate the role of two key parameters governing thermal-pressurization of pore fluids -- hydraulic diffusivity and shear-zone half-width -- on earthquake rupture dynamics, kinematic source properties and ground-motions. We conduct 3D strike-slip dynamic rupture simulations assuming a rate-and-state dependent friction law with strong velocity-weakening coupled to thermal-pressurization of pore fluids. Dynamic rupture evolution and ground-shaking are densely evaluated across the fault and Earth surface to analyze variations of rupture parameters (slip, peak slip-rate PSR, rupture speed Vr, rise time Tr), correlations among rupture parameters, and variability of peak ground velocity (PGV). Our simulations reveal how variations in thermal-pressurization affect source properties. We find that mean slip and Tr decrease with increasing hydraulic diffusivity, whereas mean Vr and PSR remain almost constant. Mean slip, PSR and Vr decrease with increasing shear-zone half-width, whereas mean Tr increases. Shear-zone half-width distinctly affects the correlation between rupture parameters, especially for parameter pairs slip-Vr, PSR-Vr and Vr-Tr. Hydraulic diffusivity has negligible effects on these correlations. Variations in shear-zone half-width primarily impact Vr, which then may affect other rupture parameters. We find negative correlation between slip and PSR, in contrast to simpler dynamic rupture models, whereas trends for other parameter pairs are in agreement. Mean PGVs decrease faster with increasing shear-zone half-width than with hydraulic diffusivity, whereas ground-motion variability is similarly affected by both parameters.